Telephony.



M. L. JOHNSON.

TELEPHONY) APPLIGATION FILED AUG. 10, 1911. RENEWED mm: 19, 1913.

1,;75,259, Patented Oct. 7, 1913.

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INVENTOR MORTON L. JOHNSQN ATTORNEY V CONNECTOR SWITCH 'MIL. JOHNSON.

TELEPHONY APPLICATION FILED we. 10, 1911. nnnnwnn mm: 19, 1913. L?5,25, Patented Oct. 7, 1913.

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ATTORNEY UNID @TATES OFFICE.

MORTON L. JOHNSON, OF CHICAGO, ILLINOIS, ASSIGNOR T0 CORWIN TELEPHONE MAN- UFACTURING COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONY.

Specification of Letters Patent.

Application filed August 1.0, 1911, Serial No. 643,842. Renewed June 19, 1913. Serial No. 774,701.

To all whom it may concern Be it known that I, Moarox L. Jonssox, citizen of the United States. residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephony, of which the following is a full, clear, concise, and exact description, reference being bad to the accompanying drawings, forming a part of this specification.

My invention relates to telephone exchange systems that include telephone lines which extend from telephone substations to an exchange where mechanism is provided for eflecting the automatic extension of telephone lincs and my invention relates particularly to such telephone exchange systems in which some of the lines are party telephone lines and in which common batteries are employed at the. exchanges.

A system equipped in accordance with the preferred embodiment of the invention includes circuit connections whereby telephonic communication may be held between the party line stations to the exclusion. of the exchange. switching mechanism for connecting the telephone at one of the party line stations in telephonic circuit with the party line and at that time serving to break the telephonic connection between the party line stations. a polarized magnet at the other party line station in high resistance bridge of the party line controlled by said switching mechanism servingt-o prevent the telephone at the party line station companion to that having said switching mechanism from becoming connected with the party line when the telephonic connection'between the party line stations is broken, switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery-at the exchange normally having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery, and means for reversing the common battery in its connection with the party line when the party line has been extended.

My invention, in its preferred embodiment, involves the adaptation of the invention covered by my companion ap lications Serial No. 628,777, filed May 22, 911, and

Serial No. 643,341, filed August 10, 1911, to those exchanges in which telephone lines are automatically extended.

My presentdnvention, while particularly adapted to those systems in which link circuits are automatically connected not only with callin lines but also with called lines. is notto be limited to exchanges in which the connecting ends of link circuits are automatically connected with called lines.

I will explain my invention more fully by reference to the accompanying drawings showing the preferred embodiment thereof as such embodiment exists in connection with an automatic telephone exchange system. Figure l of the drawings illustrating a party telephone line provided with means 'for automatically effecting the extension thereof at the exchange, while Fig. 2 represerits the exchange end of the party telephone line and automatic mechanism for etiecting its extension thereat, an automatic line being also indicated in Fig. 2 as extending from an automatic substation to the exchange.

The line illustrated in Fig. 2 extends from the automatic exchange A to the substation B. The party telephone line illustrated in Fig. 1 extends to the party line stations C, l). The means by which the telephone lines are automatically extended and are automatically brought into connection with each other are so well understood and are of such common use as to require no description, it sutiicing to state that I have indicated cir cuit interrupting mechanism 1 at each of the stations B, C and D for effecting the operation of the automatic mechanism at the exchange A, this circuit interrupting mechanism being adapted for inclusion in the telephone bridges at the stations B, C, D.

l have shown a signal receiving bell 12 in bridge of the party line at each of the stations (1 D. It. may be arranged to have one of the parties respond if the bell at his station rings for an unusual length of time, it being understood that it is the object to have the other party respond whenhis bell rings at all.

Each station is provided with a telephone receiver switch hook 13 adapted, when relieved of the weight or? the tele phone receiver M, to connect the telephone receiver and transmitter 15 in a circuit path between the switch springs 16 and 17 Each switch hook is provided with a post 18 that is depressed when the associate receiver is upon its switch hook, the limit to which such post 18 may be depressed being determined by a stop 19. The post 18 is provided with a lug 20 that engages the spring 17 and the springs 17 and 16 are mechanically united by a strut 21 of insulating material. By this arrangement the receiver, when placed upon its switch hook, is adapted to bring the springs 16 and 17 into engagement with their normal contacts, and, when the springs 16 and 17 are otherwise free to move, said springs will, by their own resilience, separate from their normal contacts and engage their alternate contacts. The mechanically united springs 16 and 17 are provided with a common extension 22 that normally lies beneath the catch 23 carried by the armature of a magnet 24, this catch serving to prevent the springs 16 and 17 from engaging their alternate contacts. The lug 20. normally overcomes the resilience of the springs 16 and 17 for the purpose of maintaining them in engagement with their normal contacts, a slight clear ance intervening between the extension 22 and the catch 23 that will permit the post 18 to rise sufiieiently, when the catch 23 is in normal position, to effect engagement between the associate switch hook and the v contact located above the same, 'such movement, however, being sufliciently restricted by the catch 23, when in normal position, to prevent the springs 16 and 17 from leaving their normal contacts and engaging their alternate contacts when the associate telephone receiver is removed from its switch hook. The manually operated switch 26 controls a gap in a bridge between the sides of the party line, which bridge includes the polarized magnet 24 that is desirably of high-resistance, say 15,000 ohms. A party line subscriber, in initiating a call for a line terminating at the exchange A, will remove his telephone from its switch hook and will also close the contacts at the switch 26 so as to include the magnet 24 in bridge of the party line to cause said magnet to be supplied with current from the common battery 2 at the exchange when having normal terminal connections with the line, whereby the catch 23 is withdrawn from engagement with the extension 22, the polarized magnet responding whenincluded incircuit with the battery 2 at the time when such battery has normal terminal connections with the line, so that the springs 16 and 17 may break connection with their normal contacts and make connection with their alternate contacts with the result that the telephone receiver, transmitter and circuit interrupting device 1 at the calling party line station are serially included in bridge of the party telephone line by way of the springs 16 and 17 and their alternate contacts, these alternate contacts being connected with difierent sides of the party line. The calling party then operates the dial mechanism at 1 to connect his party line with the line of the called party which may be station B, this operation being so well known by those skilled in the art as tr re quire no description. l/Vhen the path through the dial mechanism 1 is first closed,

the magnet 37, which will not operate through the relay 2st due to its high resistance, is operated due to the low"resistance of the telephone bridge at the calling party line station whereby this magnet 37 causes the connection of the common battery 2 at the automatic exchange tobecome reversed, whereby the magnets 24 at the party line stations will not be effectively energized so that the party line station that is compan ion to the calling party line station cannot secure connection with the party line owing to the fact that the polarized magnet at the seeking party line station will. prevent the switch springs 16 and 17 thereat from engaging their alternate contacts. It is of course understood that the very high resistance of the relay 24 is sutlicient to prevent the passage of enough current to maintain the energization of the relay 37 when current through the relay 37 depends upon the relay 24 for a path. Thus the relay 37 must energize and-denergize in response to the calling mechanism irrespective-of the presence of the relay 24. The bridge established at the seeking party .line station through the polarized magnet 24 is of such high resistance as not to interfere with or have any influence upon the exchange mechanism, so that the seeking station not only cannot establish an interfering bridge across the party telephone line, but .is also prevented from in any way interfering with the use of the party line that is desired at the callin party line station.

It may e said in passing that the battery 2, in accordance with well known and established practice, has its negative terminal normally connected through the upper winding of relay 37 with the normal contact of the upper armature switch of relay 38 and the alternate contact of the intermediate armature switch of the relay 88 and has its line station across the party line at sue station the windings of relay 37 will become eflectively energized. to operate the armature switch of this relay 37 to establish circuit through a sluggish relay 39. The relay 3!) being sluggish will not release its armature switches during the dialing operation. The upper armature switch of this relay closed when said relay is energized to establish a circuit which may be traced from ground through the upper armature switch and the winding of relay 38 whereby the negative terminal of the battery 2 is now connected with the intcrnualiate armature switch of relay I38 and the positive terminal of said battery is. connected with the upper armature switch of said relay 38. These armature switches are connected with the sides of the calling party line which are thus normallyconnected with battery 2 as indicated in Fig. 2, the battery having its con-, nection with the sides of the line reversed in the manner which has just been described when a low resistance bridge is established across the party line at a calling party line station.

it the station ll is a calling station, then, through mechanisn'i which is well known, the sides of its line become connected with the waiting contacts of the party line, assuming this to be the line that is to be called and that it is free to be called, the battery 2 then maintaining its normal relation with the called party line. Owing to the fact that the battery has its normal relation with the called party line, the party at the called party line station may, by operating the switch 26, cause the effective energization of the polarized magnet 24 to withdraw the associate catch 23 from the projection 22 to permit the called party to include his telephone in bridge of the line upon removing said telephone from its switch hook. The low resistance bridge established at the called party line station will serve to shunt sufficientcurrent from the polarized magnet 24 at the companion party line station to prevent the party at this station from obtaining connection with the party line by' operating his switch. 26 and removing his telephone from its hook.

If either of the party line stations is a called station the bell 12 atsuch called station will be caused to ring and the answering party line subscriber will repeat the operations hitherto described in eonnection' with the operations that ensue when a party line subscriber is a calling subscriber with the exception of the operation of the dial mechanism 1, thereby placing the telephone receiver and transmitter at such answering party line station in bridge of the party line. The dial mechanism 1 at the party line station companion to the called party line station is excluded from association with the party line so that the party at the seeking party line station cannot interfere with the connection of the party line that hasfbeen automatically effected at the.

exchange. The fact that the line is busy is indicated to the seeking party line subscriber by the failure of the )lunger 27 to rise above the plate 28, the extension 22 forcing this plunger above the plate 28 only when the magnet 24 responds, this magnet 24 responding only when the part-y line is free for appropriation.

.ln order to enable the subscribers at the party line stations to communicate direcfiy with each other, I preferably employ a distinctline between these stations that forms no part of the main party line, though I do not wish to be limited to this arrangement. This distinct line between the party line stations includes a conductor 29 that joins the normal contacts of the springs 17 and a. conductor 30 that joins the normal contacts of the springs 16. A battery 31 is included in one of these conductors for the purpose of supplying battery current to the telephones at the party line stations. When either party line station desires to communicate with the other, the contacts of a switch 32 are closed by the calling party to include a signal receiver 33 of the called .party in circuit, the circuit for such a signal receiver being traceable from thc battery 3] through the signal receiver 33 at the called station, the contacts of the switch 32 at the calling station back to the battery 3t by way of a portion of the conductor 29 that includes said battery. When the party line subscribers are to talk with each other the switches 26 at the party line stations are allowed to remain normal and the parties place themselves in direct telephonic com munication by way of the conductors 29 and 3t) merely'by removing the telephone receivers from their switch hooks, the telephone circuit between the stations including the conductors 29 and 30, the switch springs 16 and 17 and the normal contacts of said switch springs. During the eonversationbetween. the party line subscribers the springs 16 and 17 are held out of eugagen'ient with their alternate contacts by means of the catches 23 so that the party line proper, which extends to the exchange, is maintained out of telephonic relation with the telephones at both of the party line stations during'the establishment of telephonic connection between these stations by way of the conductors 29 and-l0, the signal receivers 12 being then amply free to receive incoming signals, while at the same time the switching mechanism at the exchange is not disturbed bv any low resistance shunt at the party line stations. In this way'telephonic communication may be held directly betwen the party line stations independently of the exchange so that this conversation may not be listened into by way of any line entering the exchange.

Now let it be assumed that the stations C,

D are located in the same place antl rat one of these stations, say station 0, is presided over by an attendant whose duty it is to assist the party at the remaining station in governing the connection of the telephone at such remaining station with the party line. As the system is organized, the party at either of the stations is adapted to assist the otl. :r in the way described, but for the sake of illustration the stat-ion C has been selected as the attendant station, it being understood that I do not limit myself to the equipment whereby each of the party line stations may supplement the other in effecting association with the party line. If the party at station D desires to call another party, say the party atstation B and wishes the attendant at station C to attend to the details of the call, the party at station D will operate the signal 33 at station 0 and have telephonic communication with the party at station C in the manner which has been described whereafter the party at station D will restore his telephone to its switch hook to await the si al to be conveyed by his signal device 33 when the called line has been secured. The attendant at station G will'remove his telephone from its switch hook and will operate the switch 26 so as to permit the springs 16 and 17 to engage their alternate contacts, in a manner which has been described, thereby to include the associate telephone receiver, transmitter and circuitinterrupter in bridge of the party line to enable the automatic connection of the called line wit-h the calling line as has been generally explained. When the called party at station B responds the party at station C will inform the called party that the party at station D desires to communicate with him whereafter the attendant at station C will close the contacts of his switch 34: to include a magnet 35 in bridge of thepart-y line, thismagnet serving to close the contacts of a-switch 36 that is in parallel with the switch 34 so that the bridge through the magnet 35 may be maintained at-36 when the contacts of the switch 34 are separated. The bridge established through the magnet 35, this magnet being desirably of high resistance, say of 1,000 ohms, affords the passage of suiiicient current from the common battery of the common battery exchange A through the relay 37 at the exchange to maintain this relay in its energized condition, whereby the switches at the automatic exchange are prevented from being released. When the attendants switch 34 is operated, the tele phone receiver and transmitter at the attendant station either has its circuit open at its switch hook or is limited to circuit rev lation with the conductors 29 and 30. When the attendant operates the switch 34 his receiver should be free of its switch hook the manner which has been described. Calling party at stat-ion D thereupon closes the contacts of his switch 26 and removes his telephone from its switch hook whereby this telephone becomes connected in bridge of the party line with the result that the bridge established at the magnet 35 is broken and the relay 37 at the exchangeis placed directly within the control of the. calling party at station D. The magnet 35 may be equipped with a signal attachment 35 to inform the operator at the attendant party line station, whichever stat-ion this-may be, when the other party line station has taken g,

the party line.

It will be observed that the party at the attendant station cannot listen in upon the connection that is now established between the calling station D and the called station B since the magnet 24 at the attendant station is shunted by the telephone receiver bridge at the station D, the catch 23 of 'the shunted magnet 24 preventing the springs 16 and 17 from leaving their normal and engaging their alternate contacts, which latter contacts have to be engaged by these springs in order to enable the attendant at station 0 to bridge the telephone at this station across the party line which is now connected with the receiver and transmitter at station D to the exclusion of the private line 29, 30 owing to the separation of. the normal contacts at station D from the springs 16 and 17 thereat. In this way, as the invention is specifically embodied, either station C or D may communicate with the other and either of these stations may have connection with the exchange by way of the party line to the exclusion of the other. On the other hand a calling station whose line terminates at the exchange is totally excluded from the telephonic circuit that intervenes directly between the stations C, D by way of the private line 29, 30, a characteristic that is of importance particularly where one of the stations C D is a called station with respect to a line entering the exchange.

The element 18, in the preferred embodiment of the invention, is manually operated through the manipulation of the associate telephone receiver which acts upon theelement- 18 through the intermediation of the inmate receiver switch book 13. I do not wish to be limited in all embodiments of the invention to the switch hook control of the ele ment 18.

While I have herein shown and particularly described the preferred embodiment of my invention I do not wish to be limited to the precise details of construction and circuit arrangement illustrated, but

Having thus described my invention I claim as new and desire to secure by Letlers Patent the following:

1. A telephone exchange system including telephone lines extending from telephone substations to an exchange where a common battery is'located and which is provided with mechanism for automaticallyextend ing the telephone lines, one of said lines being a party telephone line extending from a plurality of party line stations to said exchange; circuit connections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange; switching mechanism for connecting the telephone at one of the party line stations in telephonic circuit with the party. line and at that time serving to break the telephonic connection between the party line stations; a polarized magnet at the other party line station in high resistance bridge of the party line controlled by said switching mechanism serving to prevent the telephone at the party line station companion to that having said switching mechanism from becoming connected with-the party line when the telephonic connection between the party line stations is broken; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normall having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery; and means for reversing the common battery in its connection with the party line when the party line has been extended.

2. A telephone exchange system including telephone lines extending from telephone substations to an exchange where a common battery is located and which is provided with mechanism for automatically extending the telephone line, one orsaid lines being a party telephone line extending from a plu- 55 rality of party line stations to said exchange; -circuit connections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange; switching mechanism for con- 69 necting the telephone at one of the party line stations in telephonic circuit with the party line and at that time serving to break the telephonic connection between the party line stations; a polarized magnet at the other party line station in high resistance bridge till of the party line controlled by said switching mechanism serving to prevent the telephone at the remaining party line station from becoming connected with they party line when said telephonic connection with the party line is established; switching -mechanism for establishing and breaking has been extended.

3. A telephone exchange system including telephone lines extending from telephone substations to an exchange where a common battery is located and which is provided with mechanism for automatically extending the telephone lines, one of said lines being a party telephone line extending from a plurality of party line stations to said exchange; circuit connections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange; switching mechanism for connecting the telephone at one of the party line stations in telephonic circuit with the party line and at that time serving to break the telephonic connection between thcpartyline stations; a polarized magnet at the other party line station in high resistance bridge of the party line serving to prevent the telephone at the remaining party line station from becoming connected with the party line when said telephonic connection with the party line is established; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normally having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery; and means for reversing the common battery in its connection with the party line when the party line has been extended.

4. A telephone exchange system including telephone lines extending from telephone substations to an exchange where'a common battery is located and which is provided with mechanism for automatically extending the telephone lines, one of said lines being a party telephone line extending from a plurality of party line stations to said exchange; circuitconnections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange; switching mechanism at one of the party line stations adapted in one condition of use to take part in establishing the telephonic connection between the party line Stationsthat is independent of the exchange and in another condition of use to permit of the connection of the associate telephone with the party line; a polarized magnet at the other party line station inhigh resistance bridge of the party line where this switching mechanism is controlledlfor preventing that operation of said switching mechanism that will permit the association of the associate telephone receiver with the party line; means at the remaining party line station for governing the operation of the latter means; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normally having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery; and means for reversing the common battery in its connection with the party line when the party line has been extended.

5. A telephone exchange system including telephone lines extending from telephone substations to an exchange where a common battery is located and which is provided with mechanism for automatically extending the telephone lines, one of said lines being a party telephone line extending from a plurality of party line stations to said exchange; circuit connections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange;

switching mechanism atone of the party line stations adapted in one conditionof use to take part in establishing the telephonic connection between the party line stations that is independent of the exchange and in an other condition of use to permit of the connection of the associate telephone with the party line; a polarized magnet at the other party line station in high resistance bridge of the party line where this switching mechanism is controlled for preventing that operation of said switching mechanism that will permit the association of the associate telephone receiver with the party line; means at the remaining party line station for governing the operation of the latter means; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normally having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery; and means for reversing the common battery in its connection with the party line when the party line has been extended, there being a switch hook at the station where the afore said switching mechanism is located which serves to place said switching mechanism in condition to enable the establishment of telephonic connection between the party line stations that is exclusive of the exchange and which switch hook permits the connection of the associate telephone with the party line when said switching mechanism is free to effect this connection.

6. A telephone exchange system including telephone lines extending from telephone substations to an exchange Where a common battery is located and which is provided with mechanism for automatically extending the telephone lines, one of said lines being a party telephone line extending from a plurality of party line stations to said exchange; circuit connections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange; switching mechanism for connecting the telephone at one of the party line stations in the telephonic circuit with the party line and at that time serving to break, the telephonic connection between the party line stations; a polarized magnet at the other party line station in high resistance bridge of the party line controlled by said switching mechanism serving to prevent the telephone at the party line station companion to that having said switching mechanism from becoming connected with the party line when the telephonic connection between the party line stations is broken; switching mechanism 'for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange nor-' mally having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery; means for reversing the common battery inits connection with the party line when the party line has been extended; means for preventing operation of the switching mechanism at the exchange when telephonic communication is established between party line stations exclusively of the exchange; and means for removing the control of the latter means when telephonic connection is established between the telephone at a party line station and the party line.

7. A telephone exchange system including telephone lines extending from telephone substations to an exchange where a common battery is located and which is provided with mechanism for automatically extending the telephone lines, one of said lines being a party telephone line extending from a plurality of party line stations to said exchange; circuit connections whereby telephoniocommunication may be held between the party line stations to the exclusion of the exchange; switching mechanism for connecting the telephone at one of the party line stations in telephonic circuit with the party line and atv that time serving to break the telephonic connection between the party line stations; a polarized magnet at the other party "line station in high resistance bridge of the party line controlled by -said switching mechanism acetate serving to prevent the telephone at the remaining party line station from becomin connected with the party line when sai telephonic connection with the party line is established; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normally having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery; means for reversing'the common battery in its connection with the party line when the party line has been extended; means for preventing operation of the switching mechanism at the exchange when telephonic communication is established between party line stations exclusively of the exchange; and means for removirlg the control of the latter means when telephonic connection is established between the telephone at a party line station and the party line.

8. A telephone exchange system including telephone lines extending from telephone substations to an exchange where a common battery is located and which is provided with mechanism for automatically extending the telephone lines; one of said lines bein a party telephone line extending from a p urality of party line stations to said exchange; circuit connections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange; switching mechanism for connecting the telephone at one of the party line stations in telephonic circuit with the party line and at that time serving to break the telephonic connection between the party line stations; a polarized magnet at the other party line station in high resistance bridge of the part line serving to prevent the telephone at t e remaining party line station from becomi connected with the party line when said te ephonic connection with the party line is established; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normally having circuit relation with the party line that will enable the Cpolarized magnet to respond when include in circuit with said common battery; means for reversing the common battery in its connection wit the party line when the party line has been extended; means for preventing operation of the switching mechanism at the exchange when telephonic communication is established between arty line stations exclusively of the exc ange; and means for removing the control of the lattenmeans when telephonic connection is established between the telephone at a party line station and the arty line.

A telephone exchange system including 65 telephone lines extending from telephone relation with the party line that will enable .ing a party telephone line extending from a plurality of party line stations to said exchange; circuit .connections whereby telephonic communication may be held between I the party line stations to the exclusion of the exchange; switching mechanism atone of the party line stations adapted in one condition of use to take part in establishing the telephonic connection between the party line stations that is independent of the exchange and in another condition of use to permit of so the connection of the associate telephone with the party line; a polarized magnetat the other party line station in high resistance bridge of the party line where this switching mechanism is controlled for preventing that operation of said switching mechanism that will permit the association of the associate telephone receiver with the party line; means at thremaining party line station for governing the operation of the latter means; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normally having circuit the polarized magnet to respond when included in circuit with said common battery; means for reversing the common battery in its connection with the party line when the party line has been extended; means for preventing operation of the switching mechanism at the exchange when telephonic communication is established between party line stations exclusively of the exchange; and means for removing the control of the latter means when telephonic connection is established between the telephone at a party line station and the party line.

10. A telephone exchange system including telephone lines extending from telephone substations to an exchange where a common battery is located and which is provided with mechanism for automatically extending the telephone lines, one of said lines being a party telephone line, extending from a plurality of party line stat-ions to said exchange; circuit connections whereby telephonic communication may be held between the party line stations to the exclusion of the exchange; switching mechanism at one of the party line stations adapted in one condition of use to take part'in establishing the telephonic connection between the party line stations that is independent of the exchange and in another condition of use to permit of the con- 5 nection of the associate telephone with the party line; a polarized magnet at the other party line station in high resistance brid e of the party line where this switchin mec anism is controlled for preventing that op-' 1 0 no i eration of said switching mechanism that will permit the association of the associate telephone receiver with the party line; means at the remaining party line station for governing the operation of the latter means; switching mechanism for establishing and breaking the bridge containing said polarized magnet, the common battery at the exchange normally having circuit relation with the party line that will enable the polarized magnet to respond when included in circuit with said common battery; means for reversing the common battery in its connection with the party line when the party line has been extended, there being a switch hook at the station Where the aforesaid switching mechanism is located which serves to place said switching mechanism in condition to enable the establishment of telephonic connection between the party line stations that is exclusive of the exchange and which switch hook permits the connection of the associate telephone with the party line when said switching mechanism is free to effect this connection; means for preventing operation of the switching mechanism at the exchange when telephonic communicationis established between party line stations exclusively of the exchange; and means for removing the control of the latter means when telephonic connection is established between the telephone at a party line station andsthe party line.

In witness whereof, I hereunto subscribe mynamc this 24th day of July, A. D. 1911.

MORTON L. JOHNSON.

Witnesses E. L. WHITE, G. L. Cnoeo.

Gopies of this patent may be obtained for five cents'each, by addressing the Commissioner of Patents,

Washington, D. C. 

